Various types and configurations of seal arrangements, bushings, packing boxes, stuffing boxes, glands and the like are known for providing a seal around the rotating shaft that drives a ship's propeller, for example where the shaft penetrates through the stern of the ship from the interior to the exterior of the ship's hull. The seal arrangement must effectively prevent water from the exterior environment, i.e. from the exterior of the hull below the water line, leaking into the interior of the hull where the shaft penetrates through the hull, while still allowing the shaft to rotate. Preferably, the seal arrangement should also dissipate the frictional heat that arises due to rubbing friction of seal elements on the rotating shaft, should allow for the removal of wear particles or other contaminants from the seal arrangement, and further should provide a long operating life and allow easy maintenance.
One known type of seal arrangement uses plural seal rings spaced axially from one another along the propeller shaft in a stern tube, for example, thereby forming successive seal chambers respectively between successive neighboring ones of the seal rings. An outermost chamber can be filled with seawater, an intermediate chamber can be pressurized with a compressed gas such as compressed air, and an inner chamber can be filled with oil. The respective fluid, for example air or oil, can be supplied to and drained from the respective seal chamber through respective medium lines.
A seal arrangement for sealing a ship propeller shaft between the exterior water and the interior lubricant space, of the above described general type is known, for example, from the German patent laying-open document DE 44 34 247. The disclosed arrangement comprises a multiple seal arrangement having two seal rings oriented toward the exterior water and two seal rings oriented toward the lubricant space of the ship propeller shaft. A respective seal chamber is formed respectively between neighboring seal rings. A fluid medium can be supplied into the respective seal chamber via a respective medium supply line, and the fluid can be removed from the chamber via another respective medium return line.
As seen in the direction from the interior lubricant space toward the exterior water, this known seal arrangement has the forwardmost or first seal chamber filled with an oil, the second or middle seal chamber filled with air, and the third or aft seal chamber filled with exterior water. Because the multiple seal arrangement is arranged outside of the ship hull, the respective medium lines conveying the respective medium to and from each chamber must, at least partially sectionwise, pass through a massive housing such as a stern tube section for example, or such as a gondola or pod housing, depending on the particular type of embodiment of the ship drive arrangement. These sections of the fluid supply and return lines guided through the housing are typically individual bored holes, that each respectively correspond to a single fluid supply or return line, and that each require a technically demanding and time intensive boring operation for their formation. This is especially problematic and disadvantageous when a seal arrangement of an existing ship propeller shaft is to be upgraded, retrofitted or supplemented with additional seal chambers and/or additional medium supply and return lines. In such a situation, it becomes necessary to bore additional individual bore holes through the massive housing around the ship propeller shaft, for which the required boring or drilling operations can lead to a long out-of-service time of the ship in a service dock. Such long out-of-service times must absolutely be avoided due to the high costs and accruing losses when the ship is out of service.